Special Senses: Hearing and the Vestibular Senses Flashcards
Describe the different functions of each part of the ear.
Outer Ear: Funnel the sound waves into the ear
Middle Ear: IMPEDENCE MATCHING –> Sound wave has been moving through air, but now we are going to have it move through water
Inner Ear: Transmit the sound into Action Potentials
What is the name of the base membrane in the Organ of Corti?
Basilar Membrane
Differentiate between the composition and location of Perilymph and Endolymph.
Perilymph: Most similar to ECF (HIGH Na+, LOW K+); Located in Scala Vestibuli and Scala Tympani
Endolymph: Most similar to ICF (HIGH K+, LOW Na+); Located in the Scala Media (Cochlear Duct)
**** This gives us a Potential different between the Perilymph and Endolymph
What starts the vibration in the fluid within the cochlea?
STAPES!!!
Differentiate between high and low frequency sounds in relation to deformation fo the Basilar Membrane.
*** As the stapes hits the Oval Window, it is going to cause deformation of the Basilar Membrane
High frequency: Cause the maximum vibration of the Basilar Membrane CLOSEST to the oval window
Low frequency: Cause the maximum vibration of the Basilar Membrane FURTHEST away from the oval window (near the Helicotrema)
How do you convert the fluid vibrations in the Cochlea into Action Potentials along the Vestibulocochlear Nerve?
Bending of the OUTER Hair Cells are responsible for giving us Action Potentials!
- Each stereocilia on the hair cell is connected to another at the top by an extracellular filamentous protein (Tip Link)
- Kinocilium –> Taller than all of the other stereocilia
- Bent TOWARDS: DEPOLARIZES (opens a K+ channel); when the K+ channel opens, the K+ will ENTER the hair cell and depolarizes them (Ca2+ flows in as well)
- Bends AWAY: HYPERPOLARIZES
Describe the different structures that are involved in the Auditory Pathway to the brain:
- Ventral Pathway
- Dorsal Pathway
- Medial Superior Olive
- Lateral Superior Olive
- Inferior Colliculus
- Superior Colliculus
- Primary Auditory Cortex (A1) (Rostral vs. Caudal)
- Auditory Association Cortex
Ventral Pathway: Pitch, Timing, Freqeuncy of the Sound
Dorsal Pathway: LOCALIZING the Sound (Where was the sound generated)
Medial Superior Olive: Generates a map of the intraaural TIME differences (how the sound arrived at the two ears differently)
Lateral Superior Olive: Generates a map of ITENSITY differences
Inferior Colliculus: Suppresses information related to ECHOES and arrives at a final estimation of the sound location on the horizon
Superior Colliculus: Takes the location data from the inferior colliculus and adds the third dimension to it (VERTICAL HEIGHT)
Primary Auditory Cortex (A1): Has a tonotopic representation of the sounds - MORE ROSTRAL areas are activated by LOW frequency sounds, while CAUDAL areas recieve information about HIGH freqeuncy sounds! ALSO Loudness, modulations in volume, Rate of frequency of Modulation
Auditory Association Cortex: Interpreting different tones (the meaning of the sounds (music), identification of sound (naming), and Speech)!
Differentiate between Linear and Angular Acceleration.
Linear –> Horizontal and Vertical Movement
Angular –> Rotational around one or more planes
Which structures will detect the different types of motion (Angular/Linear)?
Linear Motion –> Utricle (Horizontal Plane) and Saccule (Vertical Plane - Jumping Up and Down)
Angular Motion –> Anterior (Falling Forward), Horizontal (Spinning motion), and Posterior (Falling Backwards) Semicircular Canal
*** Any time you are moving, the ENDOLYMPH is going to move
Describe how you get an action potential within the Vestibular Nerves.
Hair Cells are imbedded in a gelatinous mass known as the CUPULA (in the Semicircular Canals)
- Hair cells will be bent based on the action of the CUPULA!
- Movement in one direction is EXCITATORY and the other direction is INHIBITORY.
Specialized Structures:
Macula –> Utricle and Saccule
Cupula –> Semicircular Canals
Describe the Vestibular Reflexes.
*** Reflexes are designed to keep our focus on the horizon (spot directly in front of us)
If you fall FORWARD –> eyes move UP
- Superior Rectus is ACTIVE
- Inferior Rectus is INHIBITED
If you fall BACKWARD –> eyes move DOWN
- SUPERIOR OBLIQUE is ACTIVE
- INFEIROR OBLIQUE is INHIBITED
If you SPIN –> eyes rotate HORIZONTALLY until you can no longer physically focus on that spot
- Meidal Rectus* is ACTIVE and *Lateral Rectus is INHIBITED (Ipslateral Eye)
- Lateral Rectus* is ACTIVE and *Medial Rectus is INHIBITED (Contralateral Eye)
What is the role of Cortical and Cerebellar involvement in the Vestibulooptic reflexes?
Mainly to SUPPRESS the reflex to allow for VOLUNTARY control
